UB researcher Peihong Zhang and colleagues have established the
presence of a dynamic effect in defective diamonds, a finding that
will help advance the development of diamond-based quantum
information processing.

-- Diamonds with defects known as "nitrogen-vacancy centers" can
be used in applications including quantum information
processing.

-- One problem preventing scientists from fully understanding
these defective diamonds is that at the point of defect, the
high-symmetry energy configuration of the defect becomes unstable
when an electron is promoted to an excited state. This is known as
the Jahn-Teller effect.

-- Now, for the first time, researchers led by the University at
Buffalo have conducted calculations revealing how the diamond
lattice stabilizes itself at the point of defect by changing its
shape, providing new information on the consequence of such
dynamical distortion.

BUFFALO, N.Y. -- A University at Buffalo-led research team has
established the presence of a dynamic Jahn-Teller effect in
defective diamonds, a finding that will help advance the
development of diamond-based systems in applications such as
quantum information processing.

"We normally want things to be perfect, but defects are actually
very important in terms of electronic applications," said Peihong
Zhang, the UB associate professor of physics who led the study.
"There are many proposals for the application of defective
diamonds, ranging from quantum computing to biological imaging, and
our research is one step toward a better understanding of these
defect systems."

The findings deal with diamonds whose crystal structure contains
a particular defect: a nitrogen atom that sits alongside a vacant
space in an otherwise perfect lattice made only of carbon.

At the point of the imperfection -- the so-called
"nitrogen-vacancy center" -- a single electron can jump between
different energy states. (The electron rises to a higher, "excited"
energy state when it absorbs a photon and falls back to a lower
energy state when it emits a photon).

Understanding how the diamond system behaves when the electron
rises to an excited state called a "3E" state is critical to the
success of such proposed applications as quantum computing.

The problem is that at the nitrogen-vacancy center, the 3E state
has two orbital components with exactly the same energy -- a
configuration that is inherently unstable.

In response, the lattice "stabilizes" by rearranging itself.
Atoms near the nitrogen-vacancy center move slightly, resulting in
a new geometry that has a lower energy and is more stable.

This morphing is known as the Jahn-Teller effect, and until
recently, the effect's precise parameters in defective diamonds
remained unknown.

Zhang and colleagues from the Rensselaer Polytechnic Institute
in Troy, N.Y., are the first to crack that mystery. Using UB's
supercomputing facility, the Center for Computational Research, the
team conducted calculations that reveal how, exactly, the diamond
lattice distorts.

Their findings align with experimental results from other
research studies, and shed light on important topics such as how
long an excited electron at the nitrogen-vacancy center will stay
coherently at a higher energy state.

The UB-Rensselaer study was funded by the Department of
Energy.

The University at Buffalo is a premier research-intensive public
university, a flagship institution in the State University of New
York system and its largest and most comprehensive campus. UB's
more than 28,000 students pursue their academic interests through
more than 300 undergraduate, graduate and professional degree
programs. Founded in 1846, the University at Buffalo is a member of
the Association of American Universities.